Field
The described technology generally relates to an organic light-emitting diode (OLED) display.
Description of the Related Technology
Among image display devices, an organic light-emitting diode display (OLED) is a self-light-emitting type and therefore does not need to include a separate light source. Therefore, OLED technology is advantageous in terms of power consumption, and has excellent response speed, viewing angle, and contrast ratio.
An OLED display includes a plurality of pixels representing primary colors, and thus a full color palette is realized by combining these pixels. Each pixel includes an OLED and a plurality of thin film transistors to drive the OLED.
Each OLED pixel includes a pixel electrode, a common electrode, and a light-emitting layer formed therebetween. One of the pixel electrode and the common electrode is an anode electrode and the other is a cathode electrode. The common electrode is formed over the plurality of pixels and may deliver a constant voltage. The OLED display combines electrons injected from the cathode electrode with holes injected from the anode electrode in the light-emitting layer to form excitons, and emits light while the excitons emits energy.
The OLED display may be divided into a bottom emission type which emits light to a rear surface of a substrate and a top emission type which emits light to a front surface of the substrate. In the case of the top emission type of OLED display, the common electrode is formed of a transparent conductive material.
In the top emission type OLED display, internal light emitted from the light-emitting layer therein is mostly emitted outside the OLED display, but external light incident from the surroundings is partially reflected from various layers of the OLED display, and therefore an image may not be displayed properly. In particular, since a black visual characteristic deteriorates and thus a contrast ratio deteriorates, a polarizer is generally attached around an interface at which the OLED display meets the external environment to reduce the reflection of external light. As the polarizer, a linear polarizer and a circular polarizer including a ¼ wave retarder are generally used.
Display devices having a touch sensor capability are being commercially developed. The touch sensing function means a function of sensing touch information on whether external objects such as a finger and a touch pen touch a screen, a touched position, or the like, when the external objects access or touch a screen. For the touch sensing function, a touch electrode layer including a plurality of touch electrodes may be formed. The touch electrode layer also increases thickness of the display device.
Owing to the polarizer and the touch electrode layers, the thickness of the display device increases. The increase in the thickness of the display device may increase a thickness of a final product and make it difficult to implement a flexible display device.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.